This topic contains a solution. Click here to go to the answer

Author Question: How long did it take for oxygen to build up in the Earth's atmosphere to its present levels? A) ... (Read 28 times)

809779

  • Hero Member
  • *****
  • Posts: 579
How long did it take for oxygen to build up in the Earth's atmosphere to its present levels?
 
  A) at least 542 million years
  B) at least 360 million years
  C) at least 2 billion years
  D) at least 3.5 billion years

Question 2

Express the following number to three significant figures: 21.25 m
 
  What will be an ideal response?



Related Topics

Need homework help now?

Ask unlimited questions for free

Ask a Question
Marked as best answer by a Subject Expert

blakeserpa

  • Sr. Member
  • ****
  • Posts: 338
Answer to Question 1

C

Answer to Question 2

21.3 m




809779

  • Member
  • Posts: 579
Reply 2 on: Jul 27, 2018
Great answer, keep it coming :)


bigsis44

  • Member
  • Posts: 317
Reply 3 on: Yesterday
Excellent

 

Did you know?

About 3.2 billion people, nearly half the world population, are at risk for malaria. In 2015, there are about 214 million malaria cases and an estimated 438,000 malaria deaths.

Did you know?

Approximately 15–25% of recognized pregnancies end in miscarriage. However, many miscarriages often occur before a woman even knows she is pregnant.

Did you know?

Malaria mortality rates are falling. Increased malaria prevention and control measures have greatly improved these rates. Since 2000, malaria mortality rates have fallen globally by 60% among all age groups, and by 65% among children under age 5.

Did you know?

Thyroid conditions may make getting pregnant impossible.

Did you know?

The effects of organophosphate poisoning are referred to by using the abbreviations “SLUD” or “SLUDGE,” It stands for: salivation, lacrimation, urination, defecation, GI upset, and emesis.

For a complete list of videos, visit our video library